In recent years, in response to the increase in the sheer volume of information to be dealt with, a demand has arisen for higher density and larger capacity magnetic storage devices which record information. Examples of magnetic storage devices that have appeared in response to this demand are magnetic disks and magneto-optical disks. These are widely used in computers as external storage devices since, apart from the fact that they have a high density and large capacity, they can be randomly accessed.
As shown in FIG. 5, the magnetic disk comprises for example a magnetic film 22 made of a magnetic substance such as CoNiCr and formed on an Al substrate 21, and a lubricant film 23 made of lubricant material such as carbon. The magnetic film 22 and the lubricant film 23 are layered in sequence.
Information is recorded and reproduced by, for example, a magnetic head 27 attached to a flying type slider 26. When the contact-start-stop (CSS) method is used and the magnetic disk is not rotating, the flying type slider 26 presses down on the lubricant film 23 since the flying type slider 26 is suspended from a suspension 25. When the magnetic disk is rotated, a constant space 28 of approximately 0.2 .mu.m comes to be maintained between the magnetic head 27 and the magnetic disk due to the dynamic balancing of a floating force with a depressing force. The floating force is the force exerted upwards on the flying type slider 26 due to an air flow between the lubricant film 23 and the bottom side of the flying type slider 26. The depressing force is the force exerted downwards by the flying type slider 26 since it is suspended from the suspension 27.
When information recorded at high density is to be reproduced, it is desirable that the magnetic head 27 be brought as close as possible to the magnetic film 22 in order to increase the reproduction output of the magnetic head 27. Consequently, the smaller the space 28, the better. However, if the space 28 is too small, the magnetic head 27 sometimes contacts with the lubricant film 23 and, since the lubricant film 23 is thin, problems occur such as noise and damage to the magnetic film 22. Due to the fact that the contact between the magnetic head 27 and the lubricant film 23 occurs at portions projecting from the lubricant film 23, it is desirable that the surface finish of the lubricant film 23 be as fine as possible. This allows the space 28 to be reduced without damaging the magnetic film 22.
However, if the surface finish is too fine the flying type slider 26 may stick to the lubricant film 23, making it impossible for the magnetic disk to start rotating.
In order to prevent such sticking, concavities and convexities are formed on the surface of the lubricant film 23. This is done by a process generally referred to as the texturing process according to which, as shown by a partially enlarged view in FIG. 6, concavities and convexities approximately 20 nm high are formed on the Al substrate 21 by polishing the surface thereof after performing anodic oxide coating. When the magnetic film 22 and the lubricant film 23 are subsequently layered on the Al substrate 21, the lubricant film 23 acquires a concavo-convex surface.
However, a problem exists in the texturing process that a sufficient reproduced output is not achieved because an effective space 28 of more than 0.2 .mu.m becomes necessary in order to prevent the magnetic head 27 from hitting the highest convexities.